A conventional type of household electric toaster has a bread carriage that, during a toasting cycle, is held down by a releasable latch mechanism. The toasting time and the release of the bread carriage is controlled by a bimetallic element or "bimetal". The extent by which the bimetal must deflect in order to release the bread carriage is a function of the heating time and, accordingly, the degree, or shade, to which a piece of bread is toasted. The extent of bimetal deflection required to release the latch mechanism is controlled by a toast shade selector that includes a shade control knob accessible to the user. When a darker shade of toast is desired, the shade control knob is rotated so that the bimetal must deflect to a greater degree before releasing the latch mechanism which permits the bread carriage to move upwardly from its toasting position to its non-toasting position. Conversely, when a lighter shade of toast is desired, the shade control knob is rotated so that the bimetal deflects to a smaller degree before the toast carriage moves from its toasting position to its non-toasting position.
FIGS. 1 and 2 illustrate a prior art shade selector 10 having an upstanding, metal mounting bracket 12 with spaced apart plates 14 and 16 which are generally parallel to one another and interconnected at their lower ends by a base plate 18. The toast shade setting is adjusted by turning a shade control knob 20 which is frictionally secured to the outer or knob end 22 of a substantially D-shaped shade control shaft or D-shaft 24 upon which a molded plastic shade control cam element 26 is mounted for relative axial movement. Cam element 26 has a D-shaped throughbore that cooperates with the D-shaft 24 to prevent relative rotation between them. In addition cam element 26 has an outwardly facing cam surface 28 adapted to bear against a spring-biased latch plate 30 (FIG. 3) of a bread toaster 32. As is well known, shade control knob 20 is disposed on the outer end 22 of shaft 24 to enable one to turn the shade control cam element 26 in both clockwise and counterclockwise directions to adjust the toasting times.
The inner end, designated 34, of the shade control shaft 24 is of a reduced diameter and is journaled in, and projects through, an aperture 36 in the inner plate 16. The reduction in diameter creates an inwardly facing shoulder 38 that bears against the outwardly facing surface of the inner plate 16. A spring clip 40 that bears against the opposite, or inwardly facing surface, of the inner plate 16 is seated in a groove 42 at the extreme inner end of the D-shaft 24. Accordingly, the D-shaft 24 is held axially fixed to the inner plate 16 and will not be accidentally dislodged if one pulls the knob 20 off from the D-shaft 24.
The knob end 22 of the D-shaft 24 is journaled in a throughbore 43 of a hollow adjusting nut 44 which is threadedly mounted in a bore 46 in the outer plate 14. The shade control cam element 26 is pressed against the inner end face 48 of the adjusting nut 44 by a compression spring 50 coiled about the D-shaft 24. The inner end of the spring 50 bears under compression against the inner plate 16 and is thereby frictionally resisted from rotating. A washer 52 is freely rotatably disposed around the D-shaft 24 between the cam element 26 and the spring 50 to permit the cam element 26 to rotate relative to the spring 50 without having the outer end of the spring 50 abrade against the cam element 26 during rotation. In practice, the adjusting nut 44 is rotated by use of a suitable tool (not shown) to position the cam element 26 along the D-shaft 24 so that the cam element 26 can effectively be rotated to vary the toasting time and thereby the toast shade over a useful interval. This adjustment of the cam element 26 is normally done at the factory which manufactures the toaster.
The prior art toast shade selector of FIGS. and 2 is dependably effective to control the shade of toast, is durable, and is relatively inexpensive to manufacture and assemble. However, its D-shaft 24 is a relatively complex part which is typically formed by screw machining procedures. Both the D-shaft 24 and the molded plastic cam element 26 are relatively expensive to manufacture. Due to the large numbers of toasters produced each year, there is always a need to decrease the manufacturing cost wherever possible. A small savings in the cost of manufacturing a single toaster can provide the manufacturer quite substantial savings over the course of a year.